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July 9, 2009

Frozen carbon a climate change threat

by Sam Savage

An Australian-led team of scientists says it has determined the amount of frozen carbon in Earth's northern regions is more than double previous estimates.

We now estimate the deposits contain over 1.5 trillion tons of frozen carbon, about twice as much carbon as contained in the atmosphere, said Charles Tarnocai of Agriculture and Agri-Food Canada, the study's lead author.

Pep Canadell, executive director of Australia's Global Carbon Project and study co-author, said the existence of super-sized deposits of frozen carbon means any thawing of permafrost due to global warming might lead to significant emissions of carbon dioxide and methane -- both greenhouse gases.

Radioactive carbon dating shows that most of the carbon dioxide currently emitted by thawing soils in Alaska was formed and frozen thousands of years ago, University of Florida Professor Ted Schuur said. And that, he noted, demonstrates how easily carbon decomposes when soils thaw under warmer conditions.

Canadell said permafrost carbon is a wild card in efforts to predict climate change. He said evidence suggests carbon in permafrost is likely to play a significant role in the 21st century's climate.

Carbon in permafrost is found largely in northern regions including Canada, Greenland, Kazakhstan, Mongolia, Russia, Scandinavia and the United States.

The research appears in the journal Global Biogeochemical Cycles and was recently published in the journal Nature.